The present invention relates to bedding and mattresses, and more particularly to mattresses of a type including pneumatic bladders as an important support element in the construction of the mattress. The invention specifically relates to an apparatus for providing variable firmness control to beds having air mattresses as a structural feature.
Beds utilizing air mattresses as an important and functional component thereof are known in the art. The best and most recent example of such a bed may be found in U.S. Pat. No. 4,224,706, issued Sept. 30, 1980, and U.S. patent application No. 094,347, filed Nov. 14, 1979 now U.S. Pat. No. 4,306,322, both of which are owned by the assignee of the present invention. These beds relate specifically to air beds having a "closed" air system, whereas the present invention relates to an air bed having an "open" air system. By contrast, a "closed" air system in a pneumatic bed assembly incorporates an air mattress of some structure which is coupled through appropriate tubes to an air bladder, wherein a predetermined volume of air is sealably confined by the two air elements. Relative firmness of such a pneumatic bed assembly is achieved by controllably transferring some of the air volume between the mattress and the air bladder, and vice versa, and the patents above referred to achieve this result through a mechanism for controlling the total volume of the air bladder. Such a mechanism requires the confinement of the air bladder in a closed but variable volume, and includes means for increasing and decreasing the confinement volume so as to either permit air to flow from the mattress into the air bladder or to force air from the air bladder into the mattress. When air is released from the air mattress into the bladder the "feel" of the bed becomes softer, and when air is forced from the bladder into the mattress, the "feel" of the bed becomes more firm.